Rigid raft

ABSTRACT

The present invention provides a rigid raft formed of rigid composite material. The raft has an electrical system and/or a fluid system embedded therein. The raft further has a tank for containing liquid integrally formed therewith. The tank can be formed of the rigid composite material. The tank can be for a gas turbine engine.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromBritish Patent Application Number 1122140.5 filed 22 Dec. 2011, BritishPatent Application Number 1122143.9 filed 22 Dec. 2011, and BritishPatent Application Number 1203991.3 filed 7 Mar. 2012, the entirecontents of all of which are incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rigid raft formed of rigid compositematerial, and having an electrical system and/or a fluid system embeddedtherein, and particularly, but not exclusively, to a gas turbine enginerigid raft.

2. Description of the Related Art

A typical gas turbine engine has a substantial number of electricalcomponents which serve, for example, to sense operating parameters ofthe engine and/or to control actuators which operate devices in theengine. Such devices may, for example, control fuel flow, variable vanesand air bleed valves. The actuators may themselves be electricallypowered, although some may be pneumatically or hydraulically powered,but controlled by electrical signals.

Electrical power, and signals to and from the individual electricalcomponents, is commonly transmitted along conductors. Conventionally,such conductors may be in the form of wires and/or cables which areassembled together in a harness. In such a conventional harness, eachwire may be surrounded by an insulating sleeve, which may be braided orhave a braided cover.

By way of example, FIG. 1 of the accompanying drawings shows a typicalgas turbine engine including two conventional wiring harnesses 102, 104,each provided with a respective connector component 106, 108 forconnection to circuitry, which may be for example accommodated withinthe airframe of an aircraft in which the engine is installed.

The harnesses 102, 104 are assembled from individual wires and cableswhich are held together over at least part of their lengths by suitablesleeving and/or braiding. Individual wires and cables, for example thoseindicated at 110, emerge from the sleeving or braiding to terminate atplug or socket connector components 112 for cooperation withcomplementary socket or plug connector components 114 on, or connectedto, the respective electrical components.

Each conventional harness 102, 104 comprises a multitude of insulatedwires and cables. This makes the conventional harness itself bulky,heavy and difficult to manipulate. The conventional harnesses occupysignificant space within a gas turbine engine (for example within thenacelle of a gas turbine engine), and thus may compromise the design ofthe aircraft, for example the size and/or weight and/or shape of thenacelle.

Conventional harnesses comprise a large number of components, includingvarious individual wires and/or bundles of wires, supporting components(such as brackets or cables) and electrical and/or mechanicalconnectors. This can make the assembly process complicated (and thussusceptible to errors) and/or time consuming. Disassembly of theconventional harnesses (for example removal of the conventionalharnesses from a gas turbine engine during maintenance) may also becomplicated and/or time consuming. Thus, in many maintenance (or repairor overhaul) procedures on a gas turbine engine, removal and subsequentrefitting of the conventional electrical harness may account for a verysignificant portion of the operation time and/or account for asignificant proportion of the potential assembly errors.

The electrical conductors in the conventional harnesses may besusceptible to mechanical damage. For example, mechanical damage mayoccur during installation (for example through accidental piercing ofthe protective sleeves/braiding) and/or during service (for example dueto vibration). In order to reduce the likelihood of damage to theconductors in a conventional harness, the protective sleeves/braidingmay need to be further reinforced, adding still further weight andreducing the ease with which they can be manipulated. Similarly, theexposed electrical connectors used to connect one conductor to anotherconductor or conductors to electrical units may be susceptible to damageand/or may add significant weight to the engine.

Gas turbine engines contain oil tanks to provide storage for oil andallow air entrained in the scavenged oil to come out of solution andseparate. The tank is conventionally made of metal and is mounted offthe engine casings using a series of brackets and rods.

The oil leaves the tank and travels to an oil pump where it ispressurized and then distributed to various parts of the engine where itis used to lubricate the bearing chambers and gearboxes.

After use within the engine, the oil and entrained air is returned by ascavenge pump. An oil/air separator separates the oil from the air. Thelargely oil-free air is ejected overboard and the oil re-enters thetank.

A fuel-cooled oil-cooler (FCOC) comprising a heat exchanger which coolsthe oil and heats incoming fuel is generally provided. Without the FCOC,the oil would eventually overheat, degrade and fail to perform. However,it is also know to use air-oil heat exchangers (AOHEs) to cool the oilusing fan air.

The way in which the oil system elements are connected together variesfrom engine to engine. However, the oil tank is expensive and heavy as apart and due to the dedicated mounting features that it requires. Thetank also takes up space on the engine, and electrical systems have toattach to it or avoid it, which increases cost and complexity.

OBJECTS AND SUMMARY OF THE INVENTION

In a first aspect, there is provided a rigid raft, the rigid raft beingformed of a rigid material and having an electrical system and/or afluid system embedded in the rigid material, the raft further having atank for containing liquid integrally formed therewith. The rigidmaterial may be a rigid composite material. The rigid raft may be for anengine, such as a gas turbine engine.

The rigid raft may be an electrical rigid raft that includes at least apart of an electrical system comprising electrical conductors embeddedin the rigid material. Transferring electrical signals using theembedded electrical system of the rigid raft can provide a number ofadvantages over transferring electrical signals using a conventionalharness. For example, during assembly and in use, such rafts may providegreater protection to their electrical conductors than conventionalharnesses. Further, the use of such rafts may significantly reduce thebuild and maintenance times of an engine, and/or reduce the possibilityof errors occurring during such procedures. The rafts can also provideweight and size advantages over conventional harnesses. Similaradvantages accrue when fluids are transferred using the embedded fluidsystem of the rigid raft.

In addition, the integral tank provides a convenient, and potentiallyweight-, space- and cost-saving way of providing a liquid tank, such asan oil tank. For example, the integral tank allows the elimination ofdedicated mounting features for the tank.

In a second aspect, the present invention provides a gas turbine engineor gas turbine engine installation, having the raft according to thefirst aspect mounted thereto. For example, when the raft is anelectrical rigid raft that includes an electrical system comprisingelectrical conductors embedded in the rigid material, the electricalrigid raft may be part of an electrical system of the gas turbineengine; and the electrical system may further comprise a flexible cableelectrically connected between the electrical rigid raft and anothercomponent of the electrical system.

Thus, the electrical raft assembly may be a first engine installationcomponent, and the gas turbine engine may further comprise a secondengine installation component having electrical conductors. The gasturbine engine may further comprise at least one flexible cableconnected between the electrical raft assembly and the second engineinstallation component so as to electrically connect electricalconductors of the electrical raft assembly with electrical conductors ofthe second engine installation component.

The second engine installation component may be, for example, an ECU,such as an EMU or EEC. Additionally or alternatively, the second engineinstallation component may be a further electrical raft or electricalraft assembly.

Further optional features of the invention will now be set out. Theseare applicable singly or in any combination with any aspect of theinvention.

The tank may be formed of the rigid material, for example the rigidcomposite material. For example, the tank may be formed by a chambercreated in the raft during moulding or laying up of the raft.

The tank may be lined, for example with a metal liner.

The raft may be for a gas turbine engine, although the use of the rafton e.g. other types of engine is also possible. The tank may be an oiltank. Alternatively, the tank may be a fuel tank. For example, when thetank is an oil tank, the oil can be engine oil. When the tank is a fueltank, the fuel can be drainage fuel drained from a fuel manifold of theengine after engine shutdown.

The tank may have a filler cap, e.g. so that the liquid can bereplenished in the tank. The tank may have a pressure relief valve,which can help to prevent over-pressurisation of the liquid. The tankmay have a sight glass, which can allow maintenance staff to determinethe contents of the tank. The tank may have a filter for the liquid,e.g. so that the liquid can be kept free of debris.

The tank may have a liquid quantity sensor and for a liquid temperaturesensor (such as a thermocouple). The liquid quantity sensor can provideinformation about the amount of liquid left in the tank. The liquidtemperature sensor can help to prevent over-heating or under-heating ofthe liquid. Conveniently, power and/or signal cables for the or eachsensor can be embedded in the rigid material.

The tank may have a liquid pressure sensor. The tank may have one ormore magnetic chip detectors for detecting metal debris in the liquid.Such detectors can be particularly useful in relation to engine oil asthey can provide warning of e.g. bearing wear. Again power and/or signalcables for the sensor and/or the detector(s) can be embedded in therigid material.

The raft may further have a heating system for heating the liquid in thetank. Such a system can be particularly useful in relation to engineoil. For example, gas turbine engine oil tanks and systems generallyhave to pass a “de-congeal test” before being given an airworthinesscertificate. In such a test, the engine is cooled to −40° centigrade,which causes the oil to become waxy. On start-up, the engine mustsurvive without damage until sufficient heat has been transferred intothe oil to cause it to de-congeal. The test may stipulate thatde-congealing must occur within 5 minutes. However, preferably less timeis required. A reason is that in order to reduce fuel consumption duringtaxiing, there is a development at the aircraft level to tow theaircraft to the end of the runway or use electrical power rather thanthe engine thrust. Thus engines may be started only shortly beforetake-off and so have less time to heat up before going to high power.

The heating system may include one or more electrical heating elements.For example, the or each electrical heating element can be embedded inthe rigid material, e.g. on one side of the tank or on opposing sides ofthe tank. Alternatively, the or each electrical heating element can bean immersion element within the tank. Conveniently, power cables for theor each electrical heating element can be embedded in the rigidmaterial.

The rigid raft may have at least one fluid passage embedded in the rigidmaterial. The embedded fluid passage(s) may be at least a part of afluid system. At least one embedded fluid passage may be in fluidcommunication with the tank.

The tank may have a liquid inlet port and a liquid outlet port. Forexample, the inlet port may be fed by a liquid flow passage that isembedded in the rigid material, and/or the outlet port may feed a liquidflow passage that is embedded in the rigid material.

In general, the use of one or more electrical rafts/electrical raftassemblies may significantly reduce build time of an engine. Forexample, use of electrical rafts/electrical raft assemblies maysignificantly reduce the part count involved in engine assembly comparedwith a conventional harness arrangement. The number and/or complexity ofthe operations required to assemble an engine (for example toassemble/install the electrical system (or network) and/or otherperipheral components, which may be referred to in general as enginedressing) may be reduced. For example, rather than having toinstall/assemble a great number of wires and/or wiring looms together onthe engine installation, it may only be necessary to attach a relativelysmall number of electrical rafts/electrical raft assemblies, whichthemselves may be straightforward to handle, position, secure andconnect. Thus, use of electrical raft assemblies in a gas turbineinstallation may reduce assembly time and/or reduce the possibility oferrors occurring during assembly.

Use of electrical raft assemblies may provide significant advantagesduring maintenance, such as repair and overhaul. As discussed above, theelectrical rafts may be particularly quick and straightforward toassemble. The same advantages discussed above in relation to assemblyapply to disassembly/removal from the gas turbine engine. Thus, anyrepair/overhaul that requires removal of at least a part of theelectrical harness may be simplified and/or speeded up through use ofelectrical rafts as at least a part of the electrical harness, forexample compared with conventional harnesses. Use of electrical rafts(for example as part of one or more electrical raft assemblies) mayallow maintenance procedures to be advantageously adapted. For example,some maintenance procedures may only require access to a certain portionof the gas turbine engine that only requires a part of the harness to beremoved. It may be difficult and/or time consuming, or not evenpossible, to only remove the required part of a conventional harnessfrom a gas turbine engine. However, it may be relatively straightforwardto only remove the relevant electrical raft, for example by simplydisconnecting it from the engine and any other electricalrafts/components to which it is connected. Decreasing maintenance timeshas the advantage of, for example, reducing out-of service times (forexample off-wing times for engines that are used on aircraft).

The build/assembly times may be additionally or alternatively reduced bypre-assembling and/or pre-testing individual and/or combinations ofelectrical rafts and/or electrical raft assemblies prior to engineassembly. This may allow the electrical and/or mechanical operation ofthe electrical rafts to be proven before installation, therebyreducing/eliminating the testing required during engine installation.

Accordingly, there is provided (and aspects of the invention may be usedwith/as a part of) a method of servicing a gas turbine engine, themethod comprising: removing a first rigid raft from the gas turbineengine, the rigid raft incorporating at least a part of at least onecomponent or system of the gas turbine engine; and installing a second,pre-prepared, rigid raft onto the gas turbine engine in place of thefirst raft. The first and second rigid raft may be electrical harnessraft assemblies having electrical conductors embedded in a rigidmaterial. The electrical conductors may be at least a part of anelectrical system arranged to transfer electrical signals around theengine.

The electrical rafts/electrical raft assemblies may be a particularlylightweight solution for transferring electrical signals around anengine. For example, an electrical raft may be lighter, for examplesignificantly lighter, than a conventional harness required to transmita given number of electrical signals. A plurality of conductors may beembedded in a single electrical raft, whereas in a conventionalarrangement a large number of heavy, bulky wires, usually withinsulating sleeves, would be required. The reduced weight may beparticularly advantageous, for example, when used on gas turbine engineson aircraft.

Electrical rafts may be more easily packaged and/or more compact, forexample than conventional harnesses. Indeed, as mentioned above, theelectrical rafts can be made into a very wide range of shapes asdesired. This may be achieved, for example, by manufacturing theelectrical rafts using a mould conforming to the desired shape. As such,each electrical raft may be shaped, for example, to turn through atighter corner (or smaller bend radius) than a conventional harness. Theelectrical rafts may thus provide a particularly compact solution fortransferring electrical signals around a gas turbine engine.

The electrical rafts may be readily shaped to conform to neighbouringcomponents/regions of a gas turbine engine, for examplecomponents/regions to which the particular electrical raft assembly isattached, such as a fan casing or a core casing.

The electrical raft(s) may provide improved protection to the electricalconductors during manufacture/assembly of the raft/gas turbineinstallation, and/or during service/operation/maintenance of the gasturbine engine. This may result in lower maintenance costs, for exampledue to fewer damaged components requiring replacement/repair and/or dueto the possibility of extending time intervals (or service intervals)between inspecting the electrical system, for example compared with asystem using only conventional harnesses.

Any suitable material may be used for the rigid material of theelectrical raft. For example, the rigid material may be a rigidcomposite material, such as an organic matrix composite material. Such arigid composite material may be particularly stiff and/or lightweight.Thus, a rigid composite raft may be used that has suitable mechanicalproperties, whilst being thin and lightweight, for example compared withsome other materials. The rigid composite material may comprise anysuitable combination of resin and fibre as desired for a particularapplication. For example, any of the resins and/or fibres describedherein may be used to produce a rigid composite material for theelectrical raft. Any suitable fibres may be used, for example carbonfibres, glass fibres, aramid fibres, and/or para-aramid fibres. Thefibres may be of any type, such as woven and/or chopped. Any suitableresin may be used, for example epoxy, BMI (bismaleimide), PEEK(polyetheretherketone), PTFE (polytetraflouroethylene), PAEK(polyaryletherketone), polyurethane, and/or polyamides (such as nylon).

In any example of electrical raft or electrical raft assembly, at leastone of the electrical conductors embedded in the electrical raft may bean electrically conductive wire. The or each electrically conductivewire may be surrounded by an electrically insulating sleeve.

At least some (for example a plurality) of the electrical conductors maybe provided in a flexible printed circuit (FPC). Thus, at least some ofthe electrical conductors may be provided as electrically conductivetracks in a flexible substrate. The flexible printed circuit may beflexible before being embedded in the rigid material.

Providing the electrical conductors as tracks in a flexible printedcircuit may allow the size of the resulting electrical raft to bereduced further and/or substantially minimized. For example, manydifferent electrical conductors may be laid into a flexible printedcircuit in close proximity, thereby providing a compact structure. Theflexible substrate of a single flexible printed circuit may provideelectrical and/or mechanical protection/isolation to a large number ofelectrical conductors.

Any given electrical raft may be provided with one or more electricalwires embedded therein (which may be sheathed) and/or one or moreflexible printed circuits embedded therein. As such, a given electricalraft may have wires and flexible printed circuits laid therein.

It will be appreciated that the embedded electrical conductors (whetherthey are provided as embedded electrical wires or as conductive tracksin a flexible printed circuit embedded in the rigid material) may bedescribed as being fixed in position by the rigid material, for examplerelative to the rest of the electrical harness raft. It will also beappreciated that the embedded electrical conductors may be said to besurrounded by the rigid material and/or buried in the rigid materialand/or integral with (or integrated into) the rigid material.

The electrical raft (or electrical raft assembly) may be at least a partof an electrical harness for a gas turbine engine, and thus may bereferred to herein as an electrical harness raft (or electrical harnessraft assembly).

An electrical raft (or electrical raft assembly) may comprise a fluidpassage. Such a fluid passage may be embedded therein and/or otherwiseprovided thereto. The fluid passage may be part of a fluid system, suchas a gas (for example pneumatic or cooling gas/air) and/or liquid (forexample a fuel, hydraulic and/or lubricant liquid).

There is also provided a method of assembling an electrical raftassembly and/or a gas turbine engine. The method comprises preparing anelectrical raft assembly as described above and elsewhere herein. Themethod also comprises electrically and mechanically connecting theprepared electrical raft assembly to the rest of the apparatus/gasturbine engine.

Thus, there is provided a gas turbine engine or gas turbine engineinstallation (for example for an airframe) comprising an electrical raftand/or an electrical raft assembly as described above and elsewhereherein. For example, at least one electrical raft and/or electrical raftassembly may be used as part of an electrical harness for transferringelectrical signals around the engine, in the form of electrical harnessraft(s) and/or electrical harness raft assemblies.

The electrical raft may comprise one or more electrical connectors orsockets, which may be electrically connected to at least one of theembedded electrical conductors. The electrical connector or socket mayallow electrical connection of the electrical raft to other electricalcomponents, for example to other electrical rafts (either directly orindirectly, via an electrical cable or lead) or to electrical units(again, either directly or indirectly, via an electrical cable or lead).Such an electrical connector or socket may take any suitable form, andmay be at least partially embedded in the rigid electrical raft.

The environment of a gas turbine engine during operation may beparticularly severe, with, for example, high levels of vibration and/ordifferential expansion between components as the temperature changesthrough operation and as the components move relative to each other.Providing at least one flexible cable to connect an electrical raftassembly to another component may allow the electrical rafts and/orcomponents to accommodate vibration and/or relative movement, forexample of the component(s)/assemblies to which they areattached/mounted during use. For example, the flexible cable(s) (wherepresent) used to electrically connect electrical raft assemblies toother component(s) may have sufficient length to accommodate suchvibration and/or movement during use.

For example, providing separate (for example more than one) electricalraft assemblies and connecting at least some (for example at least two)of them together using at least one flexible cable may allow theelectrical rafts to accommodate vibration and/or relative movement ofthe component(s)/assemblies to which they are attached/mounted duringuse.

The electrical signals transferred by the conductors in the electricalraft, and around the engine using the electrical rafts/raft assembliesmay take any form. For example, the electrical signals may include, byway of non-limitative example, electrical power and/or electricalcontrol/communication signals and/or any other type of transmissionthrough an electrical conductor. Transmission of signals around theengine may mean transmission of signals between (to and/or from) anynumber of components/systems in the engine and/or components/system of astructure (such as an airframe) to which the gas turbine engine is (oris configured to be) connected/installed in. In other words, anelectrical raft may be used to transfer/communicate any possiblecombination of electrical signals in any part of a gas turbine engineinstallation or a related (for example electrically and/or mechanicallyconnected) structure/component/system.

An electrical raft or raft assembly may be provided in any suitablelocation/position of the gas turbine engine, for example to a mountingstructure at any suitable location. For example, the gas turbine enginemay comprise a bypass flow duct formed between an engine core and anengine fan casing (the gas turbine engine may be a turbofan engine, forexample); and the electrical raft assembly may form at least a part of aradially extending splitter (which may be referred to as a bifurcation)that extends across the bypass flow duct. In this way, an electricalraft (which may be referred to as a splitter electrical raft) mayprovide an electrical connection between a fan casing and an enginecore. By way of further example, the electrical raft assembly may beattached to the engine core case or engine fan case, for example to amounting structure on such cases.

Other components/systems of a gas turbine engine may be provided to arigid raft in any suitable manner. For example, such othercomponents/systems may be mounted on one or more rigid raft assemblies.Thus, a surface of a rigid raft may be used as a mounting surface forother gas turbine engine components/systems, such as ancillary/auxiliarycomponents/systems.

For example, an electrical unit may be mounted on an electrical raft.The electrical unit may be any sort of electrical unit, for example onethat may be provided to a gas turbine engine. For example, theelectrical unit may be any type of electronic control unit (ECU), suchas an Electronic Engine Controller (EEC) and an Engine Health MonitoringUnit (EMU). At least one (i.e. one or more) electrical unit may beattached to an electrical raft. Such an electrical raft assembly may bea particularly convenient, lightweight and/or compact way of providing(for example attaching, fixing or mounting) an electrical unit to aturbine engine. For example, the electrical unit and the electrical raftmay be assembled together (mechanically and/or electrically) beforebeing installed on the gas turbine engine, as described elsewhereherein.

An electrical raft may be provided with at least one mount on whichother components (for example auxiliary/ancillary components/systems) ofthe gas turbine engine are (or may be) mounted. The mount may be abracket, for example a bespoke bracket for the component/system mountedthereon or a conventional/standard bracket. The electrical raft mayprovide a stable, regular and convenient platform on which to mount thevarious systems/components. The combination of the installed electricalraft assembly with components/systems mounted thereon may be much morecompact and/or straightforward to assemble and/or have a greatly reducednumber of component parts, for example compared with the correspondingconventional electrical harness and separately mountedcomponents/systems.

The mounts may be used to attach any component/system to an electricalraft (and thus to the engine) as required. For example, fluid pipes fortransferring fluid around the engine may be mounted to the electricalrafts (for example mechanically mounted using a bracket), and thus tothe engine. More than one set of fluid pipes, for example for carryingdifferent or the same fluids, may be mounted on the same electricalraft.

An anti-vibration mount may be used to attach an electrical raft toanother component, thereby allowing the electrical raft to be vibrationisolated (or at least substantially vibration isolated). Using ananti-vibration mount to attach an electrical raft/assembly to a gasturbine engine for example may reduce (or substantially eliminate) theamount (for example the amplitude and/or the number/range offrequencies) of vibration being passed to the electrical raft from thegas turbine engine, for example during use. This may help to prolong thelife of the electrical raft. Furthermore, any other components that maybe attached to the electrical raft (as discussed above and elsewhereherein) may also benefit from being mounted to the gas turbine enginevia the anti-vibration mounts, through being mounted on the electricalraft. For example, the reduced vibration may help to preserve theelectrical contact between the electrical raft and any electrical unitconnected thereto. As such, any components (such as an electrical unitmounted to the electrical raft) that would conventionally be mounteddirectly to the gas turbine engine and require at least a degree ofvibration isolation no longer require their own dedicated anti-vibrationmount. Thus, the total number of anti-vibration mounts that are requiredto assemble an engine may be reduced. This may reduce the number ofparts required and/or the time taken to assemble an engine or engineinstallation and/or reduce the total assembled weight and/or reduce thelikelihood of errors occurring during assembly.

Furthermore, components that are conventionally mounted to an enginewithout anti-vibration mounts (for example because of the weight and/orcost penalty), but which are now mounted to an electrical raft (forexample to a mounting surface of the electrical raft), may benefit fromvibration isolation without any weight/cost/assembly time penalty. Thismay reduce the possibility of damage occurring to such components and/orincrease their service life. Such components may include, for example,ignitor boxes (used to provide high voltage power to engine ignitors),and pressure sensors/switches, for example for fluid systems such asoil, air, fuel, pneumatics and/or hydraulics.

Further optional features of the invention are set out below.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of examplewith reference to the accompanying drawings in which:

FIG. 1 shows a gas turbine engine with a conventional harness;

FIG. 2 shows a cross-section through a gas turbine engine having rigidrafts in accordance with the present invention;

FIG. 3 shows a perspective view of a flexible printed circuit;

FIG. 4 shows a side view of the flexible printed circuit of FIG. 3;

FIG. 5 shows a schematic of an electrical raft prior to assembly;

FIG. 6 shows a cross-section normal to the axial direction through a gasturbine engine having rigid rafts in accordance with the presentinvention;

FIG. 7 shows schematically a cross-sectional view of an embodiment of arigid electrical raft in accordance with the present invention, the rafthaving a tank for containing engine oil integrally formed therewith; and

FIG. 8 shows schematically a cross-sectional view of a variant of theraft of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 2, a ducted fan gas turbine engine generallyindicated at 10 has a principal and rotational axis X-X. The engine 10comprises, in axial flow series, an air intake 11, a propulsive fan 12,an intermediate pressure compressor 13, a high-pressure compressor 14,combustion equipment 15, a high-pressure turbine 16, and intermediatepressure turbine 17, a low-pressure turbine 18 and a core engine exhaustnozzle 19. The engine also has a bypass duct 22 and a bypass exhaustnozzle 23.

The gas turbine engine 10 works in a conventional manner so that airentering the intake 11 is accelerated by the fan 12 to produce two airflows: a first air flow A into the intermediate pressure compressor 13and a second air flow B which passes through the bypass duct 22 toprovide propulsive thrust. The intermediate pressure compressor 13compresses the air flow A directed into it before delivering that air tothe high pressure compressor 14 where further compression takes place.

The compressed air exhausted from the high-pressure compressor 14 isdirected into the combustion equipment 15 where it is mixed with fueland the mixture combusted. The resultant hot combustion products thenexpand through, and thereby drive the high, intermediate andlow-pressure turbines 16, 17, 18 before being exhausted through thenozzle 19 to provide additional propulsive thrust. The high,intermediate and low-pressure turbines 16, 17, 18 respectively drive thehigh and intermediate pressure compressors 14, 13 and the fan 12 bysuitable interconnecting shafts.

The gas turbine engine 10 shown in FIG. 2 shows two electrical raftassemblies 600 according to the invention, at least one of which may bea rigid raft in accordance with the invention. As such, the gas turbineengine 10 is in accordance with the present invention. Each electricalraft assembly 600 comprises an electrical raft 200. The electrical rafts200 may be used to transmit/transfer electrical signals (or electricity,including electrical power and/or electrical control signals) around theengine and/or to/from the engine 10 from other components, such ascomponents of an airframe. The function and/or construction of eachelectrical raft 200 and electrical raft assembly 600 may be as describedabove and elsewhere herein.

In FIG. 2, each electrical raft 200 (which may be referred to hereinsimply as a raft 200 or an electrical harness raft 200) comprises atleast one electrical conductor 252 embedded in a rigid material 220,which may be a rigid composite material.

The electrical conductors 252 in the electrical raft 200 may be providedin a harness 250, which may be a flexible printed circuit board (or FPC)250.

An example of an FPC 250 in which the electrical conductors 252 may beprovided is shown in greater detail in FIGS. 3 and 4. FIG. 3 shows aperspective view of the FPC 250, and FIG. 4 shows a side view.

Such an FPC 250 may comprise a flexible (for example elasticallydeformable) substrate 255 with conductive tracks 252 laid/formedtherein. The FPC 250 may thus be deformable. The FPC 250 may bedescribed as a thin, elongate member and/or as a sheet-like member. Sucha thin, elongate member may have a major surface defined by a length anda width, and a thickness normal to the major surface. In the exampleshown in FIGS. 3 and 4, the FPC 250 may extend along a length in thex-direction, a width in the y-direction, and a thickness (or depth orheight) in the z-direction. The x-direction may be defined as the axialdirection of the FPC. Thus, the x-direction (and thus the z-direction)may change along the length of the FPC 250 as the FPC is deformed. Thisis illustrated in FIG. 4. The x-y surface(s) (i.e. the surfaces formedby the x and y directions) may be said to be the major surface(s) of theFPC 250. In the example shown in FIGS. 3 and 3, the FPC 250 isdeformable at least in the z direction, i.e. in a directionperpendicular to the major surface. FPCs may be additionally ofalternatively deformable about any other direction, and/or may betwisted about any one or more of the x, y, or z directions.

The flexible substrate 255 may be a dielectric. The substrate materialmay be, by way of example only, polyamide. As will be readily apparent,other suitable substrate material could alternatively be used.

The conductive tracks 252, which may be surrounded by the substrate 255,may be formed using any suitable conductive material, such as, by way ofexample only, copper, copper alloy, tin-plated copper (or tin-platedcopper alloy), silver-plated copper (or silver-plated copper alloy),nickel-plated copper (or nickel-plated copper alloy) although othermaterials could alternatively be used. The conductive tracks 252 may beused to conduct/transfer electrical signals (including electrical powerand electrical control signals) through the rigid raft assembly (orassemblies) 200, for example around a gas turbine engine 10 and/orto/from components of a gas turbine engine and/or an airframe attachedto a gas turbine engine.

The size (for example the cross-sectional area) and/or the shape of theconductive tracks 252 may depend on the signal(s) to be transmittedthrough the particular conductive track 252. Thus, the shape and/or sizeof the individual conductive tracks 252 may or may not be uniform in aFPC 250.

The example shown in FIGS. 3 and 4 has six conductive tracks 252 runningthrough the substrate 255. However, the number of conductive tracks 252running through a substrate 255 could be fewer than six, or greater thansix, for example tens or hundreds of tracks, as required. As such, manyelectrical signals and/or power transmission lines may be incorporatedinto a single FPC 250.

A single FPC 250 may comprise one layer of tracks, or more than onelayer of tracks, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more than 10layers of tracks. An FPC may comprise significantly more than 10 layersof tracks, for example at least an order of magnitude more layers oftracks. In this regard, a layer of tracks may be defined as being aseries of tracks that extend in the same x-y surface. Thus, the exampleshown in FIGS. 3 and 4 comprises 2 layers of tracks, with each layercomprising 3 tracks 252.

An electrical raft 200 may be manufactured using any suitable method.For example, the rigid material 220 may initially be provided as layersof flexible material, such as (by way of example only) layers of fibreand resin compound. This flexible material may be placed into a mould,for example having a desired shape. Other components (such as fluidpipes 210 and/or the electrical conductors 252, which may be embedded ina FPC 250) may also be placed into the mould, for example between layersof the flexible material from which the rigid material 220 is ultimatelyformed. Parts of the mould may have any suitable form and/orconstruction, for example that could be readily removed when theelectrical raft 200 is formed into the desired shape.

FIG. 5 shows components of an example of an electrical raft 200 prior toone method of construction. The electrical conductors 252 are providedbetween two layers of material 230, 240 that, after construction, formthe rigid material 220. Some of the electrical conductors 252 areprovided in an FPC 250. The material 230, 240 may be a fibre and resincompound, as described elsewhere herein. Such a fibre and resin compoundmay, after suitable treatment (for example heat treatment), produce therigid composite material 220. In the example of FIG. 5, the fibre andresin compound is formed of a sheet of interwoven fibres, or strands.The strands in FIG. 5 extend in perpendicular directions, although thestrands may extend in any one or more directions as required. Thestrands/fibres may be pre-impregnated (or “pre-pregged”) with the resin.

Prior to any treatment, both the first and second layers 230, 240 andthe electrical conductors 252 may be flexible, for example supple,pliable or malleable. As such, when the layers 230, 240 and theelectrical conductors 252 are placed together, they may be moulded, orformed, into any desired shape. For example, the layers 230, 240 and theelectrical conductors 252 may be placed into a mould (which may be ofany suitable form, such as a glass or an aluminium mould) having thedesired shape. The desired shape may be, for example, a shape thatcorresponds to (for example is offset from) a part of a gas turbineengine, such as, by way of example only, at least a part of a casing,such as an engine fan casing or engine core casing. This may enable thefinal raft to adopt shapes that are curved in two-dimensions orthree-dimensions.

Any suitable method could be used to produce the electrical raft 200.For example, the strands/fibres need not be pre-impregnated with theresin. Instead, the fibres/strands could be put into position (forexample relative to electrical conductors 252/FPC 250) in a dry state,and then the resin could be fed (or pumped) into the mould. Such aprocess may be referred to as a resin transfer method. In someconstructions no fibre may be used at all in the rigid material 220.

During construction, an integral tank 704 (not shown in FIG. 5 butdescribed by way of example below in relation to FIGS. 8 and 9) may beformed in the electrical raft 200 (or indeed in any rigid raft). Forexample, an integral tank 704 may be formed by using a suitably shapedmould.

FIG. 6 is a schematic showing a cross-section perpendicular to thedirection X-X of a gas turbine engine comprising electrical raftassemblies 600A-600G. Any one of the electrical raft assemblies600A-600G may comprise any or all of the features of an electrical raftassembly 600 as described above, for example. Thus, for example, any oneof the electrical raft assemblies may comprise an electrical raft 200(not labelled for raft assemblies 600E-600G for simplicity only) havingelectrical conductors 252 (not labelled in FIG. 6 for simplicity only)embedded therein. Some or all of the electrical raft assemblies600A-600G (which may collectively be referred to as electrical raftassemblies 600) comprise a mounting fixture for attaching the respectiveassembly 600 to a mounting structure.

Any one or more of the electrical rafts 200/electrical raft assemblies600 shown in FIG. 6 may have a tank for containing liquid integrallyformed therewith, although such an integral tank is not shown in FIG. 6for simplicity. Thus, any one or more of the electrical rafts200/electrical raft assemblies 600 shown in FIG. 6 may have an integraltank 704 as described below by way of example in relation to FIGS. 7 and8.

The mounting structure is part of a fan case 24 for electrical raftassemblies 600A-600D, part of a bifurcation splitter that radiallycrosses a bypass duct 22 for electrical raft assemblies 600E and part ofan engine core case 28 for electrical raft assemblies 600F and 600G.However, it will be appreciated that an electrical raft assembly 600could be mounted in any suitable and/or desired location on a gasturbine engine.

In FIG. 6, two electrical raft assemblies 600A, 600C are shown as havingan electrical unit 300 mounted on the respective electrical raft 200.However, any (or none) of the electrical raft assemblies 600A-600G mayhave an electrical unit 300 mounted to the respective electrical raft200.

As mentioned herein, each of the electrical rafts 200 associated withthe electrical raft assemblies 600A-600G shown in FIG. 6 comprises oneor more electrical conductors 252 embedded therein. However, any one ormore of the electrical rafts 200 may be replaced with a raft that doesnot comprise electrical conductors 252. Such a raft would not be anelectrical raft 200, but may otherwise be as described elsewhere herein,for example it may be a rigid raft that may have components/systems(such as, by way of example only, fluid systems, such as pipes) mountedthereon and/or embedded therein and an integral tank formed in the rigidmaterial. Thus, for example, a gas turbine engine in accordance with thepresent invention may have a combination of electrical rafts 200 andnon-electrical rafts.

An electrical raft 200 may comprise an electrically conductive groundingor screen layer 260, as shown in the electrical rafts 200 shown in FIG.6. However, it will be appreciated that electrical rafts 200 accordingto the invention and/or for use with the invention need not have such anelectrically conductive grounding or screen layer 260. Where anelectrically conductive grounding or screen layer 260 is present, anelectrically conductive fastener 310 may be used to fasten, or fix, theelectrical unit 300 (where present) to the electrical raft 200. This mayallow the electrical unit 300 to be electrically grounded. It will alsobe appreciated, however, that electrical rafts 200 according to theinvention and/or for use with the invention need not have such anelectrically conductive fastener 310.

The arrangement of electrical raft assemblies 600A-600G shown in FIG. 6is by way of example only. Alternative arrangements, for example interms of number, size, shape and/or positioning, of electrical raftassemblies 600A-600G may be used. For example, there need not be sevenelectrical raft assemblies, the assemblies may or may not be connectedtogether, and the rafts could be provided to (for example mounted on)any one or more components of the gas turbine engine. Purely by way ofexample only, connection between electrical raft assemblies 600A-600Dmounted on the fan casing 24 to the electrical raft assemblies 600F,600G mounted on the core casing 28 may be provided at least in part bymeans other than an additional electrical raft assembly 600E, forexample using wire conductors with insulating sleeves. By way of furtherexample, one or more electrical raft assemblies 600 may additionally oralternatively be provided to the nose cone, structural frames orelements within the engine (such as “A-frames”), the nacelle, the fancowl doors, and/or any connector or mount between the gas turbine engine10 and a connected structure (which may be at least a part of astructure in which the gas turbine engine 10 is installed), such as thepylon 500 between the gas turbine engine 10 and an airframe (not shown).

Any one or more of the electrical rafts of the electrical raftassemblies 600A-600G may have a fluid passage 210 embedded thereinand/or provided thereto. The fluid passage 210 may be part of a fluidsystem, such as a gas (for example pneumatic or cooling gas/air) and/orliquid (for example a fuel, hydraulic and/or lubricant liquid). In theFIG. 6 example, three of the electrical rafts (of electrical raftassemblies 600A, 600B, 600C) comprise a fluid passage 210 at leastpartially embedded therein. The electrical raft of assembly 600C alsohas a fluid passage 285 (which may be for any fluid, such as thoselisted above in relation to embedded passage 210) mounted thereon. Sucha mounted fluid passage 285 may be provided to any electrical raft, suchas those of electrical raft assemblies 600A-600G shown in FIG. 6. Thefluid passages 210, 285 shown in FIG. 6 may be oriented in an axialdirection of the engine 10. However, fluid passages may be oriented inany direction, for example axial, radial, circumferential or acombination thereof. Any of the fluid passages may be in fluidcommunication with a tank that may be integral with the respective raft200.

Any of the electrical raft assemblies 600A-600G (or the respectiveelectrical rafts 200 thereof) may have any combination of mechanical,electrical and/or fluid connections to one or more (for example 2, 3, 4,5 or more than 5) other components/systems of the gas turbine engine 10and/or the rest of the gas turbine engine 10. Examples of suchconnections are shown in FIG. 6, and described below, but otherconnectors may be used. For example, electrical raft assemblies 600(and/or non-electrical rafts) may be connected together (or to othercomponents) using any combination of electrical, fluid and/or mechanicalconnectors. Thus, any of the connections 290A/290B, 291-297 shown inFIG. 6 may be any combination of electrical, fluid and/or mechanicalconnection. Alternatively, electrical raft assemblies 600 (and/ornon-electrical rafts) may be standalone, and thus may have no connectionto other rafts or components.

A connection 291 is shown between the electrical rafts of the assemblies600A and 600D. The connection 291 may comprise an electrical connection.Such an electrical connection may be flexible and may, for example, takethe form of a flexible printed circuit such as the flexible printedcircuit 250 shown in FIGS. 3 and 4. Such a flexible electricalconnection may be used to electrically connect any electrical raftassembly 600 to any other component, such as another electrical raftassembly 600. A connection 297 (which may be or comprise an electricalconnection) is provided between the electrical raft of the assembly 600Aand a part of an airframe, or airframe installation 500, which may, forexample, be a pylon. Similarly, a fluid and/or mechanical connection 296may additionally or alternatively be provided between the airframe 500and another electrical raft of the assembly 600C. As shown in FIG. 6,other electrical and/or fluid connections 292, 293, 294, 295 may beprovided between electrical rafts 200 (or assemblies 600) and othercomponents, such as other electrical rafts 200 (or assemblies 600).

A direct connection 290A, 290B may be provided, as shown for examplebetween the electrical rafts of the assemblies 600B and 600C in the FIG.6 arrangement. Such a direct connection 290A, 290E may comprise aconnector 290A provided on (for example embedded in) one electrical raft200 connected to a complimentary connector 290B provided on (for exampleembedded in) another electrical raft 200. Such a direct connection 290A,2908 may, for example, provide fluid and/or electrical connectionbetween the two electrical rafts assemblies 600B, 600C.

It will be appreciated that many alternative configurations and/orarrangements of electrical raft assemblies 600 and gas turbine engines10 comprising electrical raft assemblies 600 other than those describedherein may fall within the scope of the invention. For example,alternative arrangements of electrical raft assemblies 600 (for examplein terms of the arrangement, includingnumber/shape/positioning/constructions, of mounting fixtures, thearrangement/shape/positioning/construction of the electrical rafts 200,the type and/or positioning of components (if any) mounted to/embeddedin the electrical rafts 200, the rigid material 220 and the electricalconductors 252) may fall within the scope of the invention and may bereadily apparent to the skilled person from the disclosure providedherein. Alternative arrangements of connections (for example mechanical,electrical and/or fluid) between the electrical (or non-electrical)rafts and/or raft assemblies and between the electrical (ornon-electrical) rafts or raft assemblies and other components may fallwithin the scope of the invention and may be readily apparent to theskilled person from the disclosure provided herein. Furthermore, anyfeature described and/or claimed herein may be combined with any othercompatible feature described in relation to the same or anotherembodiment.

FIG. 7 shows schematically a cross-sectional view of an embodiment of arigid electrical raft 702 in accordance with the present invention. Theraft is mounted to the fan case 24 of the engine by raft locationformations 706 and has an integral tank 704 for containing an enginefluid, such as engine oil or fuel. Advantageously, the tank does notrequire separate location formations for mounting to the engine. Also,the weight, cost, reliability and robustness of the tank can be improvedcompared with conventional, stand-alone tanks.

The raft may have the position, structure and features of any one of therafts or raft assemblies described above in relation to FIGS. 2 to 6.The raft 702 in the FIG. 7 example includes an electrical systemcomprising electrical conductors (not shown) embedded in the plasticmatrix composite material of the raft. Electrical connectors 726 andflexible cables 728, connect the electrical conductors to othercomponents of the engine. The oil tank has a composite body like therest of the raft, and can be created by making a chamber within the raftduring moulding or laying up of the raft.

The raft 702 has a metal liner, which helps to prevent leakage from thetank and provides increased strength and robustness.

The tank 704 has a filler cap 708 which includes a pressure reliefvalve, and a sight glass 710. It also has a thermocouple-based oiltemperature sensor 712 and a quantity sensor 714 for measuring the oillevel 716 in the tank. The leads for these sensors can be embedded inthe raft and integrated with the electrical system of the raft, reducingtheir susceptibility to accidental and vibration-induced damage.

The tank 704 forms a protrusion on the outer side of the raft 702. Aninlet port 718 to the tank is formed at the outer side of the base ofthe tank, and an outlet port 720 from the tank is formed at the innerside of the base of the tank. The outlet port feeds a flow passage 722which extends through the raft. A FCOC or AOHE heat exchanger (notshown) can be located beneath the tank to cool the oil entering the tankthrough the inlet port.

Other features such as electronic magnetic chip detectors, oil filters,and pressure sensors can be incorporated into the raft 702, but are notshown in FIG. 7.

FIG. 8 shows schematically a cross-sectional view of a variant of theraft of FIG. 7. The variant has the same features as the raft of FIG. 7,but also includes an electrical heating element 724 which is embedded inthe raft 702 at the inner wall of the tank 704. In this way, the oil inthe tank can be de-congealed, for example in cold weather, usingelectrical power from a ground cart or auxiliary power unit beforeengine start-up. After heating the oil to a sufficiently hightemperature, the engine can be started, and because the oil pump drawsoil from the tank and pumps it around the system, the de-congeal timefor the entire oil system can be significantly reduced, lowering therisk of damage that may occur to engine parts through operation withcongealed oil.

The heating element 724 can operate using electrical resistance andcurrent to generate heat. It can line one side of the tank asillustrated in FIG. 8, or more than one side. Another option (not shown)is for a heating element to penetrate the tank 704 as an immersionheater. The heating element can be controlled via the engine electroniccontrol or aircraft systems, and can be automatic or require pilotaction. Power leads for the heating element can be embedded in the raftand integrated with the electrical system of the raft.

Where reference is made herein to a gas turbine engine, it will beappreciated that this term may include a gas turbine engine/gas turbineengine installation and optionally any peripheral components to whichthe gas turbine engine may be connected to or interact with and/or anyconnections/interfaces with surrounding components, which may include,for example, an airframe and/or components thereof. Such connectionswith an airframe, which are encompassed by the term “gas turbine engine”as used herein, include, but are not limited to, pylons and mountingsand their respective connections. The gas turbine engine itself may beany type of gas turbine engine, including, but not limited to, aturbofan (bypass) gas turbine engine, turbojet, turboprop, ramjet,scramjet or open rotor gas turbine engine, and for any application, forexample aircraft, industrial, and marine application. Raft assembliessuch as any of those described and/or claimed herein may be used as partof any apparatus, such as any vehicle, including land, sea, air andspace vehicles, such as motor vehicles (including cars and busses),trains, boats, submarines, aircraft (including aeroplanes andhelicopters) and spacecraft (including satellites and launch vehicles).

While the invention has been described in conjunction with the exemplaryembodiments described above, many equivalent modifications andvariations will be apparent to those skilled in the art when given thisdisclosure. For example, a fuel drainage tank could be integrated withinthe raft, the tank being used to accept fuel drained from the fuelmanifold after engine shutdown, thereby ensuring that soak back of heatdoes not overheat the drained fuel, allowing it to lacquer the pipes ordegrade into solids that can cause blockages and damage in the engineburners. Accordingly, the exemplary embodiments of the invention setforth above are considered to be illustrative and not limiting. Variouschanges to the described embodiments may be made without departing fromthe spirit and scope of the invention.

We claim:
 1. A gas turbine engine comprising: a rigid raft being formedof a rigid material, the rigid raft comprising: multiple electricalconductors embedded in the rigid material, the multiple electricalconductors being at least a part of an electrical system of the gasturbine engine; and a tank that provides a liquid to a fluid system, thetank being integrally formed with the rigid raft.
 2. The gas turbineengine according to claim 1, wherein the tank is formed of the rigidmaterial.
 3. The gas turbine engine according to claim 1, wherein therigid material is a rigid composite material.
 4. The gas turbine engineaccording to claim 1, wherein the tank is lined.
 5. The gas turbineengine according to claim 1, comprising at least one fluid passageembedded in the rigid material, the least one fluid passage being atleast a part of the fluid system.
 6. The gas turbine engine according toclaim 5, wherein the at least one fluid passage is in fluidcommunication with the tank.
 7. The gas turbine engine according toclaim 1, wherein: the tank has a liquid inlet port and a liquid outletport.
 8. The gas turbine engine according to claim 1, wherein the tankhas at least one of the following: a liquid quantity sensor and a liquidtemperature sensor.
 9. The gas turbine engine according to claim 1,wherein the rigid raft further comprises a heating system for heatingthe liquid in the tank.
 10. The gas turbine engine according to claim 9,wherein the heating system includes at least one electrical heatingelements.
 11. The gas turbine engine according to claim 10, wherein theat least one electrical heating element is embedded in the rigidmaterial and electrically connected to at least one of the multipleelectrical conductors, such that electrical power for the at least oneelectrical heating element is provided by the multiple electricalconductors.
 12. The gas turbine engine according to claim 1, wherein thetank is an oil tank or a fuel tank.
 13. The gas turbine engine accordingto claim 1, wherein: the electrical system further comprises a flexiblecable electrically connected between the rigid raft and anothercomponent of the electrical system.
 14. The gas turbine engine accordingto claim 7, wherein: the inlet port is fed by a liquid flow passage thatis embedded in the rigid material.
 15. The gas turbine engine accordingto claim 7, wherein: the outlet port feeds a liquid flow passage that isembedded in the rigid material.